1. Field of Invention
The present invention relates to a broadcast short message service(SMS) execution method in a mobile communication system, more particularly, to the method for executing a broadcast short message service so as to distribute effectively the load of paging channels by improving the existing method.
2. Background of the Related Art
Generally, the cellular mobile communication system of code division multiple access(CDMA) has been designed so as to have a flexible signal system and control structure. Therefore, a system expansion is easily made in the mobile communication system and the additional function and capacities in the next generation communication system are achieved. For these purposes, 64 channels are assigned to one FA in a base station of the CDMA cellular mobile communication system. Among the 64 channels, one is assigned to a pilot channel, one is assigned to a synchronization channel, seven channels are assigned to paging channels, and the other channels are assigned to traffic channels. The paging channels deliver the information from a base station to a mobile station by message. There is system information, paging, command, channel assignment, etc., in the important message.
However, in most countries where the CDMA cellular mobile communication system is in use, some of the seven paging channels are used for their most traffic.
Furthermore, every mobile station receives the broadcast short messages concerning with the information about stocks, weather and sports through these paging channels. In other words, a broadcast short message service agent broadcasts various kinds of broadcast short message information to all mobile stations through common paging channels in a predetermined time. Each mobile station selectively receives only the short message information that a mobile station user requests a short message service agent to send. The received information is displayed in the mobile station. Therefore, the short message information about stocks, weather, sports, etc., is periodically provided to the mobile station user through the paging channels.
FIGS. 1a to 1c are the charts showing channel slots of executing a conventional broadcast short message service in a mobile communication system.
Referring to the FIGS. 1a to 1c, the conventional broadcast short message service is provided by one paging channel at the same time as a general paging information.
FIG. 1a shows the slot structure of paging channels whose one period consists of N-paging channel slots (one slot is 80 ms). Each conventional mobile station can repeatedly do the search operation during the paging channel slot time (for example, 80 ms) allocated to itself in each paging period( for example, 5.12 seconds) in order to decide whether or not there is an information for itself. For example, FIG. 1 a is to show that a mobile station allocated to a slot f can do the search operation to verify if there is an information for itself.
On the contrary, FIG. 1b shows the structure of the paging channel slots for the broadcast short message service whose one period is constructed on the N_brdcast_sms paging channel slots(80 ms unit). The period of the paging channel slot of the broadcast short message service consists of N_brdcast_sms slots more than N-paging by three. In other words, as shown in FIG. 1b, the information about the type(A1, B1, C1, D1, E1, F1) and the number of the broadcast short message information is included in the first slot(0) among three slots(0, 1, 2).
Therefore, when the broadcast short message service is provided in a base station and a broadcast short message service agent is requested broadcasting of the broadcast short message information, each base station receives a reference information of the broadcast short message service and repeatedly makes it included in the first slot of the paging channel of each mobile station. The practical short message information(A1-F1) is broadcast just after the reference information has been loaded.
Furthermore, in a single paging channel slot time of a mobile station, both paging information and broadcast short message information may be requested. In this case, the base station gives a priority to the broadcast short message information as shown in FIG. 1c and broadcasts the broadcast short message information (A2-F2) on the preferential basis. The paging information is delayed by one period and then is broadcast in the corresponding slot (f2) in the next period since the current structure of modem chips used in conventional mobile terminals allows that a single mobile station can search only one channel during any special paging channel slot time.
However, when the broadcast short message service is performed in the conventional mobile communication system described above, the CDMA mobile communication system based on the standardization IS-95 cannot have a dedicated channel for the broadcast short message service. Therefore, the broadcast short message service is done by the paging channel. However, this broadcast short message service is performed without difficulties in the early stage in which the number of the mobile communication network subscribers is small. As the number of the subscribers is continually increased and both kinds and broadcasting periods of the broadcast short message services get great varieties, many kinds of problems have come out when essential functions of the paging channels are executed.
When a base station receives both a paging information and a broadcast short message at the same time in one paging channel time for a single mobile station, each base station gives a priority to the broadcast short message information and broadcasts the broadcast short message through the paging channel on the preferential basis. The paging information is delayed by one period and is broadcast in the corresponding paging channel slot time in the next period. Therefore, in the case that both the paging information and the broadcast short message information are simultaneously broadcast in each paging channel slot of a single mobile station, the process load of the paging channel of the base station is increased and the original processing operation of the paging channel information is not achieved effectively and timely. Furthermore, a single mobile station cannot simultaneously process two kinds of information. This problem will get more and more difficult as the number of subscribers who want to use the broadcast short message service is increased.
Accordingly, the present invention is directed to solve these problems of the conventional techniques and is to provide a broadcast short message service execution and control method which can provide the broadcast short message service by allocating one of the currently unoccupied reserve paging channels to a dedicated channel of the broadcast short message service when the broadcast short message service is executed.
Another object of the present invention is to provide a broadcast short message broadcasting service execution method that when a base station is requested to simultaneously broadcast both the paging information and the broadcast short message information into the paging channel slot of the corresponding mobile terminal, executes first the broadcast short message service by allocating one of the currently unoccupied reserve paging channels to a dedicated channel of the broadcast short message service and then broadcasts the paging information through the original paging channel.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the broadcast short message service execution method in a mobile communication system includes the step of deciding if the received radio signal is the paging information about an arbitrary mobile station, the short message information or the information consisted of both said paging information and said short message information, the step of informing a corresponding mobile station of the reference information for the short message through paging channels when said deciding step indicates that said short message information is received, the step of broadcasting said short message information after moving to one of currently unoccupied paging channels, the step of deciding if the reference information of said short message service is included in said paging information by searching said paging channels by a predetermined period, and according to the presence of the reference information of said short message service, the step of receiving the short message information by moving from said paging channels to the channel which completes the transmission of said short message information.
In the case that both paging information and short message information requested to be transmitted to a single mobile station are simultaneously received, all the steps described above are first executed and then said paging information is broadcast to the corresponding mobile station through said paging channel in the next paging channel period which is allocated to said mobile station.
According to the feature of the present invention, in the case that a broadcast short message information is broadcast from a base station to every mobile station, the existing paging channel is not used for the broadcasting. Instead, one of the currently unoccupied paging channels is assigned to a dedicated channel. Since the broadcast short message information is broadcast to every mobile station through this dedicated channel, the load of the paging channel is effectively distributed and reduced.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.